L-Cysteine

[somedud]

"We review here the possible mechanisms of neuronal degeneration caused by L-cysteine, an odd excitotoxin. L-Cysteine lacks the omega carboxyl group required for excitotoxic actions via excitatory amino acid receptors, yet it evokes N-methyl-D-aspartate (NMDA) -like excitotoxic neuronal death and potentiates the Ca2+ influx evoked by NMDA. Both actions are prevented by NMDA antagonists. One target for cysteine effects is thus the NMDA receptor. The following mechanisms are discussed now: (1) possible increase in extracellular glutamate via release or inhibition of uptake/degradation, (2) generation of cysteine alpha-carbamate, a toxic analog of NMDA, (3) generation of toxic oxidized cysteine derivatives, (4) chelation of Zn2+ which blocks the NMDA receptor-ionophore, (5) direct interaction with the NMDA receptor redox site(s), (6) generation of free radicals, and (7) formation of S-nitrosocysteine. In addition to these, we describe another new alternative for cytotoxicity: (8) generation of the neurotoxic catecholamine derivative, 5-S-cysteinyl-3,4-dihydroxyphenylacetate (cysdopac)."

Does this dictate neurotoxicity? If so then why is it one of the main amino acids in a mood improving complex?

 

[hamhurricane]

Thanks for posting this. I was totally unaware that Cysteine had this excitotoxic effect, I definitely regret having taken it as much as I have. I always thought it was benign. It has also been established to have a number of beneficial neuroprotective effects so I would be curious what other ADDers have to say about its potential toxicity...

 

[atara]

In addition to these, we describe another new alternative for cytotoxicity: ( generation of the neurotoxic catecholamine derivative, 5-S-cysteinyl-3,4-dihydroxyphenylacetate (cysdopac)."

This is interesting. It is possible that the 5-cysteinyl derivative of alpha-methyldopamine may be more toxic than aMD itself. That would explain why 5-methyl-MDA is not observed to be neurotoxic: it doesn't form a 5-cysteinyl derivative, since the 5-position is blocked by a methyl group.

Perhaps 5-fluoro-MDA is something to try.

 

[somedud]

So, in a sense would you say that L-Cysetine HCl has a different mechanism of action? I.e. Not toxic.

Also it states it's toxic oxidatives (products of oxidizing), is this the only mechanism of it's neurotoxicty, intiling one to believe a good daily antioxidant should completely protect agaisnt oxidatives stress, or is there more to it's toxicity?

Excuse my ignorance of the advanced terminology and lack of understanding. I'm just curious, as Ill quit this program I'm with if that's the case.

 

[asecin]

is Acetyl-L-Cysteine same excitotoxic chemical ?cuz NAC is said to be most potent antioxidant so im confused now if it probably its pretty bad for you...

 

[somedud]

^^^ no it's not, L-Cysetine is a different form of derivative .

Bump, I'd really like to hear someone input who can clearify this one for me! I havnt found much regarding it besides this study, and would be quickly ceasing use if it's exitoxic.

 

[atara]

I doubt dietary cysteine has any excitotoxicity. It's one of the 20 major amino acids -- not a likely toxic candidate. Cysteine injected into the brain or nervous tissues might be excitotoxic, though!